Material handling equipment, such as front end loaders to which the present invention is directed, have been available for a number of years. A typical example of a compact unit of this type is disclosed in U.S. Pat. No. 3,722,724 by Richard P. Blakely and assigned to the assignee of the present invention. To the extent that the above-mentioned patent describes the power train and the operation of the loader, the above-mentioned patent is incorporated herein by reference.
In general, such off-road or material handling machines consist of an elongated body supported by a pair of wheels. The engine compartment is adjacent the rear end of the body and the operator's compartment is adjacent the front end. A pair of stanchions or uprights are fixably secured to the body adjacent the opposite sides of the engine compartment and extend upwardly therefrom. A pair of lift arms are pivotally connected at one end about a common pivot axis on the respective uprights. The arms extend generally downwardly along opposite sides of the body in close proximity to the operator's compartment and terminate at a material handling element at the front of the body and ahead of the front set of wheels. Because the material handling element, usually a bucket, is positioned ahead of the wheels, the lift arms are ordinarily two-piece affairs with a relatively long straight arm extending from the uprights and a relatively short straight arm joined to the free end of the long arm and pointing downwardly towards the front end of the body where it joins the material handling element. The bend in the lift arms allows the lift arms to go over and around the front pair of wheels.
The material handling element is pivoted between a "roll-back" and "dump" positions by a hydraulically operated linkage mechanism that is controlled by the operator seated in the operator's compartment. Pivotal movement of the bucket is accomplished through a fluid ram that has one end pivotally connected to the bucket at a location spaced from the pivotal connection to the free ends of the lift arms and an opposite end connected to the lift arms at a location laterally offset from the longitudinal axis of the downwardly directed short, straight arm. The raising and lowering of the lift arms and the bucket relative to the uprights is normally accomplished through a second pair of fluid rams located between the uprights and the long, straight arm portion of the lift arms.
The loaders just described are characterized in that they are usually supported by four identical wheels or tires with the two tires on each side relatively close to each other. Loaders of this type are relatively small and are normally used in locations where maneuverability and turning space is severely restricted. Consequently, the material handling element must be placed as close as possible to the front end of the machine. Once the position of the material handling element is fixed, the location of the lift arms is determined. These lift arms must of necessity extend beyond the front set of wheels if they are to lift the material handling element from the ground. Conventionally, this has been accomplished by the two-piece lift arm structure previously described. Because of this angular arrangement between the short, straight arm and the long, straight arm portion of the lift arm, the joint between the two arms is relatively high stressed. It would be desirable from a fabrication and strength of materials standpoint to form each lift arm from a single piece of structural steel.
While it would be possible to have a straight line, single piece lift arm structure passing outboard or inboard the front set of wheels, this has not been adapted in commercial designs for several reasons. All other factors remaining the same, if the lift arms were placed outboard of the front set of wheels, the overall width of the machine would of necessity be increased. Similarly, if the lift arms were placed inboard the front set of wheels, either the size operator's compartment would have to be reduced or the front set of wheels placed further outboard to make room for the lift arms. In each case, the overall wheel base or effective width of the machine is increased. Any increase in width affects the maneuverability and turning radius of the machine. Consequently, it has been industry practice to use a two-piece or bent lift arms. Industry has expressed a long felt but unsatisfied need for a loader having one piece straight lift arms yet having the same maneuverability as a loader having the piece lift arms.